POJ 3180 The Cow Prom strong connectivity Component

Water problem, direct sticker code.

POJ 3180//sep9 #include <iostream> #include <stack> using namespace std;
const int maxn=10024;
const int maxm=50048;
int SUM[MAXN]; 
int HEAD[MAXN],DFN[MAXN],LOW[MAXN],INS[MAXN],BELONG[MAXN];
Stack<int> s; struct edge{int v,next;}
EDGE[MAXM];

int n,m,e,t,cnt;
	void Tarjan (int u) {dfn[u]=low[u]=++t;
	S.push (U);
	Ins[u]=1;
		for (int i=head[u];i!=-1;i=edge[i].next) {int v=edge[i].v;
			if (dfn[v]==0) {Tarjan (v);
		Low[u]=min (Low[u],low[v]);		
	}else if (ins[v]==1) low[u]=min (Low[u],dfn[v]);
	} int k;
		if (Low[u]==dfn[u]) {++cnt;
			do{K=s.top ();
			S.pop ();	
			ins[k]=0;
		belong[k]=cnt;	
	}while (Low[k]!=dfn[k]);		
} return;
	} int main () {int n,m;
 	scanf ("%d%d", &n,&m);  
  	e=0;  
   	memset (head,-1,sizeof (head));  
    memset (dfn,0,sizeof (DFN));  
	memset (ins,0,sizeof (INS));
		while (m--) {int A, B;
		scanf ("%d%d", &a,&b);
	edge[e].v=b;edge[e].next=head[a];head[a]=e++;
	} t=cnt=0; for (int i=0;i<n;++i) if (!dfn[i]) Tarjan (i);
	memset (sum,0,sizeof (sum));
	for (int i=0;i<n;++i) ++sum[belong[i]];
	int ans=0;
	for (int i=1;i<=cnt;++i) if (sum[i]>1) ++ans;
	printf ("%d", ans);	
return 0;  }